JPS6026613A - Roll for transferring hot metallic billet - Google Patents

Abstract

PURPOSE:To prevent the fracture of a hot metallic billet as a product without spoiling the quality thereof by subjecting the surface in the body part of a roll to hardening to a prescribed pattern by laser light thereby forming a brittle layer. CONSTITUTION:The body part 11a of a roll 11 for transferring a hot billet is hardened to a prescribed pattern by laser light to form an axially extending hardened part at a prescribed interval in the circumferential direction. The part 12 consists of an embrittle layer 12a on the surface having the structure consisting mainly of martensite, a heat affected zone 12b and an unaffected zone 12c. The layer 12a is formed to a prescribed depth, for example, about 0.5mm.. Fine dispersion type cracks are then generated in the layer 12a and propagate axially at prescribed intervals along the hardening pattern. The thermal stress generated on the surface of the roll 11 is thus decreased and the propagation of the cracks C are stopped by the dispersion type cracks in the part 12, by which the fracture of the roll 11 is prevented.

Description

Detailed Description of the Invention (Technical Part! l!P) This invention relates to a roll for transferring hot metal pieces, and more particularly, to a roll for transferring hot metal pieces, and more specifically, a crank which forms an embrittlement layer in a predetermined pattern on the surface layer of the roll body. The present invention relates to a roll for transferring hot metal pieces that prevents the roll from being continuous over the entire circumference and prevents the roll from breaking.

(Prior art) Rolls for transferring hot metal pieces are repeatedly heated by contact with high-temperature materials and cooled by cooling water, which generates thermal stress.In addition, rolls for transferring hot metal pieces generate thermal stress due to repeated heating due to contact with high-temperature materials and cooling due to cooling water, and stress due to bending moment (bending stress ) occurs. Thermal stress acts in the axial direction and the circumferential direction and is particularly noticeable on the roll surface layer where the temperature gradient is significant, and the bending stress acts in the axial direction and has a maximum value at the surface. As a result, cranks occur on the surface layer of the body of the roll, and the cracks develop and continue in the circumferential direction due to the synergistic effect of the thermal stress and bending stress, and also develop in the axial direction. There was a problem of having to reuse them.

Conventionally, in order to solve this problem, a tool for transferring hot metal pieces [1] was developed in Japanese Patent Application Laid-open No. 1983-1.
This is proposed in Publication No. 35008. This LSI tool for transferring hot metal pieces has grooves engraved along the axial direction at required intervals between surfaces, and the circumferential growth of cracks is stopped by the grooves to prevent breakage. ing. 'J Nawara,
This roll for transferring hot metal pieces was created by focusing on the fact that thermal stress decreases as you move toward the roll axis, which has a small slope of 61h. By forming this, the stress acting in the circumferential direction as well as the stress acting in the axial direction is reduced and breakage is prevented.

However, in such conventional rolls for transferring hot metal pieces, grooves are formed on the surface of the body, so the surface of the hot metal piece pressed by this roll has grooves corresponding to the grooves. There was a problem in that the protrusions were engraved, impairing the quality of the hot metal piece as a product.

(Objective and Structure of the Invention) The present invention was made in view of the above-mentioned problems, and in order to prevent breakage without impairing the quality of the hot metal piece as a product, a predetermined pattern is formed on the surface of the roll body. The present invention provides a roll for transporting hot metal pieces in which an embrittled layer corresponding to the pattern is formed by surface hardening with a laser beam along the pattern.

This roll for transferring hot metal pieces has a brittle layer.
Also, since residual stress is generated due to quenching, if the above thermal stress and ttb'=fI6 are generated,
Distributed fine cracks are generated on the surface layer of the roll body along the embrittlement layer or pattern. Therefore, there is no concentration of stress on the roll surface layer, and there is no longer any continuous rippling or tsuku over the entire circumference!
- Prevents breakage of the rod. In addition, with this roll for transferring hot metal pieces, there is no need to form uneven parts such as grooves on the surface of the I:1-ru body, so defects such as unevenness on the hot metal pieces are avoided. There is no life.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 and FIG. 2 are diagrams showing one embodiment of the present invention.

First, to explain the structure, in FIG. 1, reference numeral 11 indicates a l-1-roll for transferring a hot metal piece, and the roll 11 is not shown; 1
1a, and a rotating shaft 11b protruding from both axial sides 111 of the body portion na. The body portion 11a of the roll 11 is hardened in a predetermined pattern using laser light. In other words, the hardened portion 12 by this laser beam
(schematically shown by solid lines in FIG. 1) extend in the axial direction and are formed at predetermined intervals in the circumferential direction.

As shown in FIG. 2a, this hardened part 12 includes a brittle embrittlement 7i12a whose main structure is martensite, which is hardened by being irradiated with a laser beam, and an embrittled layer 12a and an unaffected part 12.
and a heat affected zone 12b between the embrittlement layer 12a and
is formed to a predetermined depth, for example, approximately 0°5*m).

The hardness Flv of the embrittlement layer 12a when hardened by laser light under predetermined conditions is shown in FIG. 2 for reference. This figure 2 corresponds to figure 2 a, and measurement points M,
, M2 , M3 , M-4, Ms , M9 , M7,
Ms is the position shown in FIG. 2a.

Next, the effect will be explained.

In such a roll for transferring hot metal pieces, the embrittlement layer 12a is fragile, and residual stress is generated due to the hardening treatment with laser light, so when thermal stress and bending stress occur, the embrittlement layer 12a Fine distributed cracks are generated in the crack, and these distributed cracks propagate in the axial direction at predetermined intervals along the pattern of laser hardening.

Therefore, the thermal stress generated on the surface layer of the roll 11 is reduced and no large stress occurs, and as shown in FIG. Since the progress is stopped and the cracks C no longer continue to grow in the circumferential direction, breakage of the cracks C is prevented.

Furthermore, since the distributed crank generated in the embrittlement layer 12a is minute, there is no imprinting of irregularities or the like on the hot metal piece, and the quality of the hot metal piece as a product is not impaired.

Note that the bending stress generated in roll J1 has a maximum value near the center of roll II, and breakage of roll 11 occurs at roll 1.
It goes without saying that since the occurrence of breakage occurs frequently in the central part of A1, even if the hardening with laser light is applied only to the vicinity of the central part A1, a sufficient effect of preventing breakage can be obtained.

3 to 5 show other embodiments of the invention.

Note that the same parts as in the embodiment described above are denoted by the same reference numerals, and the explanation thereof will be omitted.

In these examples, hardening was performed using laser light in different patterns. The roll 11 for transferring hot metal pieces shown in FIG. 3 is hardened with a laser beam in a mesh pattern, and the roll 11 for transferring hot metal pieces shown in FIG. The hot metal piece transfer roll 11 shown in FIG.
It is hardened with a laser beam in a tortoiseshell pattern.

In these rolls 11 for transferring hot metal pieces, it is possible to prevent cranks caused by thermal stress and bending stress from developing and continuing in the circumferential direction, and breakage thereof can be prevented, as in the above-described embodiments. .

(Effects of the Invention) As explained above, in the roll for transferring hot metal pieces of the present invention, since the embrittlement layer is formed in a predetermined pattern on the surface layer of the roll body, thermal stress and bending stress This prevents the crank from progressing, preventing it from breaking.

[Brief explanation of the drawing]

1 to 2 are diagrams showing a roll for transferring hot metal pieces according to an embodiment of the present invention, in which FIG. 1 is an overall view, FIG. 2a is a sectional view of a main part, and FIG. is a diagram showing the hardness of the embrittlement layer. 3 to 5 are overall views showing rolls for transferring hot metal pieces according to other embodiments of the present invention. 1l-=-Roll for transferring hot metal pieces, IIa--Roll body, 12-----1 Hardened part, 12a--1 Brittle bottom. Patent applicant Fuji Kogyo Co., Ltd. Representative Patent Attorney Arigagun Part

Claims (1)

[Claims] 1. A roll for transporting hot metal pieces, characterized in that the surface of the roll body is hardened by laser light along a predetermined pattern to form an embrittled layer.